<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<script>
    var num = 10;
    num = 20;
    console.log(num)

    //const 定义常量
    const num2 = 1;
    console.log(num2)
    num2 = 11;
</script>
<body>

</body>
</html>